Geochronological and isotopic evidence for early Proterozoic crust in the eastern Arabian Shield

We report zircon U-Pb, feldspar common Pb, whole-rock Sm-Nd, and Rb-Sr data from sample Z-103, a fine-grained granodiorite from the Jabal Khida region of the Saudi Arabian Shield (lat 21°19′N; long 44°50′W). The measurements yield conclusive evidence for continental crust of early Proterozoic age (∼1,630 Ma) at that locality. Furthermore, lead-isotope data indicate an even earlier, perhaps Archean, crustal history for the source of the lower Proterozoic rocks.